//------------------------------------------------------------------------------
// <copyright file="querybuilder.cs" company="Microsoft">
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// </copyright>                                                                
// <owner current="true" primary="true">Microsoft</owner>
//------------------------------------------------------------------------------

namespace MS.Internal.Xml.XPath {
    using System;
    using System.Xml;
    using System.Xml.XPath; 
    using System.Diagnostics;
    using System.Collections;
    using System.Collections.Generic;
    using FT = Function.FunctionType;

    internal sealed class QueryBuilder {
        // Note: Up->Doun, Down->Up:
        //       For operators order is normal: 1 + 2 --> Operator+(1, 2)
        //       For pathes order is reversed: a/b -> ChildQuery_B(input: ChildQuery_A(input: ContextQuery()))
        // Input flags. We pass them Up->Down. 
        // Using them upper query set states wich controls how inner query will be built.
        enum Flags {
            None      = 0x00,
            SmartDesc = 0x01,
            PosFilter = 0x02,  // Node has this flag set when it has position predicate applied to it
            Filter    = 0x04,  // Subtree we compiling will be filtered. i.e. Flag not set on rightmost filter.
        }
        // Output props. We return them Down->Up. 
        // These are properties of Query tree we have built already.
        // These properties are closely related to QueryProps exposed by Query node itself.
        // They have the following difference: 
        //      QueryProps describe property of node they are (belong like Reverse)
        //      these Props describe acumulated properties of the tree (like nonFlat)
        enum Props {
            None        = 0x00,
            PosFilter   = 0x01,  // This filter or inner filter was positional: foo[1] or foo[1][true()]
            HasPosition = 0x02,  // Expression may ask position() of the context
            HasLast     = 0x04,  // Expression may ask last() of the context
            NonFlat     = 0x08,  // Some nodes may be descendent of otheres
        }

        // comment are aproximate. This is my best understanding:
        private string query;
        private bool allowVar;
        private bool allowKey;
        private bool allowCurrent;
        private bool needContext;
        private BaseAxisQuery firstInput; // Input of the leftmost predicate. Set by leftmost predicate, used in rightmost one

        private void Reset() {
            parseDepth = 0;
            needContext = false;
        }
        
        private Query ProcessAxis(Axis root, Flags flags, out Props props) {
            Query result = null;
            if (root.Prefix.Length > 0) {
                needContext = true;
            }
            firstInput = null;
            Query qyInput; {
                if (root.Input != null) {
                    Flags inputFlags = Flags.None;
                    if ((flags & Flags.PosFilter) == 0) {
                        Axis input = root.Input as Axis;
                        if (input != null) {
                            if (
                                root.TypeOfAxis == Axis.AxisType.Child &&
                                input.TypeOfAxis == Axis.AxisType.DescendantOrSelf && input.NodeType == XPathNodeType.All
                            ) {
                                Query qyGrandInput;
                                if (input.Input != null) {
                                    qyGrandInput = ProcessNode(input.Input, Flags.SmartDesc, out props);
                                } else {
                                    qyGrandInput = new ContextQuery();
                                    props = Props.None;
                                }
                                result = new DescendantQuery(qyGrandInput, root.Name, root.Prefix, root.NodeType, false, input.AbbrAxis);
                                if ((props & Props.NonFlat) != 0) {
                                    result = new DocumentOrderQuery(result);
                                }
                                props |= Props.NonFlat;
                                return result;
                            }
                        }
                        if (root.TypeOfAxis == Axis.AxisType.Descendant || root.TypeOfAxis == Axis.AxisType.DescendantOrSelf)  {
                            inputFlags |= Flags.SmartDesc;
                        }
                    }

                    qyInput = ProcessNode(root.Input, inputFlags, out props);
                } else {
                    qyInput = new ContextQuery();
                    props = Props.None;
                }
            }

            switch (root.TypeOfAxis) {
            case Axis.AxisType.Ancestor:
                result = new XPathAncestorQuery(qyInput , root.Name, root.Prefix, root.NodeType, false);
                props |= Props.NonFlat;
                break;
            case Axis.AxisType.AncestorOrSelf:
                result = new XPathAncestorQuery(qyInput, root.Name, root.Prefix, root.NodeType, true);
                props |= Props.NonFlat;
                break;
            case Axis.AxisType.Child:
                if ((props & Props.NonFlat) != 0) {
                    result = new CacheChildrenQuery(qyInput, root.Name, root.Prefix, root.NodeType);                                                                                                           
                } else {
                    result = new ChildrenQuery(qyInput, root.Name, root.Prefix, root.NodeType);
                }
                break;
            case Axis.AxisType.Parent:
                result = new ParentQuery(qyInput, root.Name, root.Prefix, root.NodeType);                        
                break;
            case Axis.AxisType.Descendant:
                if ((flags & Flags.SmartDesc) != 0) {
                    result = new DescendantOverDescendantQuery(qyInput, false, root.Name, root.Prefix, root.NodeType, /*abbrAxis:*/false);
                } else {
                    result = new DescendantQuery(qyInput, root.Name, root.Prefix, root.NodeType, false, /*abbrAxis:*/false);
                    if ((props & Props.NonFlat) != 0) {
                        result = new DocumentOrderQuery(result);
                    }
                }
                props |= Props.NonFlat;
                break;
            case Axis.AxisType.DescendantOrSelf:
                if ((flags & Flags.SmartDesc) != 0) {
                    result = new DescendantOverDescendantQuery(qyInput, true, root.Name, root.Prefix, root.NodeType, root.AbbrAxis);                                                            
                } else {
                    result = new DescendantQuery(qyInput, root.Name, root.Prefix, root.NodeType, true, root.AbbrAxis);
                    if ((props & Props.NonFlat) != 0) {
                        result = new DocumentOrderQuery(result);
                    }
                }
                props |= Props.NonFlat;
                break;
            case Axis.AxisType.Preceding:
                result = new PrecedingQuery(qyInput, root.Name, root.Prefix, root.NodeType);
                props |= Props.NonFlat;
                break;
            case Axis.AxisType.Following:
                result = new FollowingQuery(qyInput, root.Name, root.Prefix, root.NodeType);
                props |= Props.NonFlat;
                break;
            case Axis.AxisType.FollowingSibling:
                result = new FollSiblingQuery(qyInput, root.Name, root.Prefix, root.NodeType);
                if ((props & Props.NonFlat) != 0) {
                    result = new DocumentOrderQuery(result);
                }
                break;
            case Axis.AxisType.PrecedingSibling:
                result = new PreSiblingQuery(qyInput, root.Name, root.Prefix, root.NodeType);
                break;
            case Axis.AxisType.Attribute:
                result = new AttributeQuery(qyInput, root.Name, root.Prefix, root.NodeType);
                break;
            case Axis.AxisType.Self:
                result = new XPathSelfQuery(qyInput, root.Name, root.Prefix, root.NodeType);
                break;
            case Axis.AxisType.Namespace:
                if ((root.NodeType == XPathNodeType.All || root.NodeType == XPathNodeType.Element || root.NodeType == XPathNodeType.Attribute) && root.Prefix.Length == 0) {
                    result = new NamespaceQuery(qyInput, root.Name, root.Prefix, root.NodeType);
                } else {
                    result = new EmptyQuery();
                }
                break;
            default:
                throw XPathException.Create(Res.Xp_NotSupported, query);
            }

            return result;
        }
        
        private bool CanBeNumber(Query q) {
            return (
                q.StaticType == XPathResultType.Any || 
                q.StaticType == XPathResultType.Number
            );
        }        

        private Query ProcessFilter(Filter root, Flags flags, out Props props) {
            bool first = ((flags & Flags.Filter) == 0);

            Props propsCond;
            Query cond = ProcessNode(root.Condition, Flags.None, out propsCond);

            if (
                CanBeNumber(cond) ||
                (propsCond & (Props.HasPosition | Props.HasLast)) != 0
            ) {
                propsCond |= Props.HasPosition;
                flags |= Flags.PosFilter;
            }

            // We don't want DescendantOverDescendant pattern to be recognized here (in case descendent::foo[expr]/descendant::bar)
            // So we clean this flag here:
            flags &= ~Flags.SmartDesc;
            // ToDo: Instead it would be nice to wrap descendent::foo[expr] into special query that will flatten it -- i.e.
            //       remove all nodes that are descendant of other nodes. This is very easy becuase for sorted nodesets all children 
            //       follow its parent. One step caching. This can be easyly done by rightmost DescendantQuery itsef.
            //       Interesting note! Can we garatee that DescendantOverDescendant returns flat nodeset? This defenetely true if it's input is flat.

            Query qyInput = ProcessNode(root.Input, flags | Flags.Filter, out props);

            if (root.Input.Type != AstNode.AstType.Filter) {
                // Props.PosFilter is for nested filters only. 
                // We clean it here to avoid cleaning it in all other ast nodes.
                props &= ~Props.PosFilter; 
            }
            if ((propsCond & Props.HasPosition) != 0) {
                // this condition is positional rightmost filter should be avare of this.
                props |= Props.PosFilter;
            }

            /*merging predicates*/ {
                FilterQuery qyFilter = qyInput as FilterQuery;
                if (qyFilter != null && (propsCond & Props.HasPosition) == 0 && qyFilter.Condition.StaticType != XPathResultType.Any) {
                    Query prevCond = qyFilter.Condition;
                    if (prevCond.StaticType == XPathResultType.Number) {
                        prevCond = new LogicalExpr(Operator.Op.EQ, new NodeFunctions(FT.FuncPosition, null), prevCond);
                    }
                    cond = new BooleanExpr(Operator.Op.AND, prevCond, cond);
                    qyInput = qyFilter.qyInput;
                }
            }

            if ((props & Props.PosFilter) != 0 && qyInput is DocumentOrderQuery) {
                qyInput = ((DocumentOrderQuery)qyInput).input;
            }
            if (firstInput == null) {
                firstInput = qyInput as BaseAxisQuery;
            }
            
            bool merge   = (qyInput.Properties & QueryProps.Merge  ) != 0;
            bool reverse = (qyInput.Properties & QueryProps.Reverse) != 0;
            if ((propsCond & Props.HasPosition) != 0) {
                if (reverse) {
                    qyInput = new ReversePositionQuery(qyInput);
                } else if ((propsCond & Props.HasLast) != 0) {
                    qyInput = new ForwardPositionQuery(qyInput); 
                }
            }

            if (first && firstInput != null) {
                if (merge && (props & Props.PosFilter) != 0) {
                    qyInput = new FilterQuery(qyInput, cond, /*noPosition:*/false);
                    Query parent = firstInput.qyInput;
                    if (! (parent is ContextQuery)) { // we don't need to wrap filter with MergeFilterQuery when cardinality is parent <: ?
                        firstInput.qyInput = new ContextQuery();
                        firstInput = null;
                        return new MergeFilterQuery(parent, qyInput);
                    }
                    firstInput = null;
                    return qyInput;
                }
                firstInput = null;
            }
            return new FilterQuery(qyInput, cond, /*noPosition:*/(propsCond & Props.HasPosition) == 0);
        }

        private Query ProcessOperator(Operator root, out Props props) {
            Props props1, props2;
            Query op1 = ProcessNode(root.Operand1, Flags.None, out props1);
            Query op2 = ProcessNode(root.Operand2, Flags.None, out props2);
            props = props1 | props2;
            switch (root.OperatorType) {
            case Operator.Op.PLUS   :
            case Operator.Op.MINUS  :
            case Operator.Op.MUL    :
            case Operator.Op.MOD    :
            case Operator.Op.DIV:
                return new NumericExpr(root.OperatorType, op1, op2);
            case Operator.Op.LT     :
            case Operator.Op.GT     :
            case Operator.Op.LE     :
            case Operator.Op.GE     :
            case Operator.Op.EQ     :
            case Operator.Op.NE     :
                return new LogicalExpr(root.OperatorType, op1, op2);
            case Operator.Op.OR     : 
            case Operator.Op.AND    : 
                return new BooleanExpr(root.OperatorType, op1, op2);
            case Operator.Op.UNION  :
                props |= Props.NonFlat;
                return new UnionExpr(op1, op2);
            default : return null;
            }            
        }

        private Query ProcessVariable(Variable root) {
            needContext = true;
            if (! allowVar) {
                throw XPathException.Create(Res.Xp_InvalidKeyPattern, query);
            }
            return new VariableQuery(root.Localname, root.Prefix);
        }

        private Query ProcessFunction(Function root, out Props props) {
            props = Props.None;
            Query qy = null;
            switch (root.TypeOfFunction) {
            case FT.FuncLast:
                qy = new NodeFunctions(root.TypeOfFunction, null);
                props |= Props.HasLast;
                return qy;
            case FT.FuncPosition:
                qy = new NodeFunctions(root.TypeOfFunction, null);
                props |= Props.HasPosition;
                return qy;
            case FT.FuncCount:
                return new NodeFunctions(FT.FuncCount,
                    ProcessNode((AstNode)(root.ArgumentList[0]), Flags.None, out props)
                );
            case FT.FuncID:
                qy = new IDQuery(ProcessNode((AstNode)(root.ArgumentList[0]), Flags.None, out props));
                props |= Props.NonFlat;
                return qy;
            case FT.FuncLocalName:
            case FT.FuncNameSpaceUri:
            case FT.FuncName:
                if (root.ArgumentList != null && root.ArgumentList.Count > 0) {
                    return new NodeFunctions(root.TypeOfFunction,
                        ProcessNode((AstNode)(root.ArgumentList[0]), Flags.None, out props)
                    );
                } else {
                    return new NodeFunctions(root.TypeOfFunction, null);
                }
            case FT.FuncString:
            case FT.FuncConcat:
            case FT.FuncStartsWith:
            case FT.FuncContains:
            case FT.FuncSubstringBefore:
            case FT.FuncSubstringAfter:
            case FT.FuncSubstring:
            case FT.FuncStringLength:
            case FT.FuncNormalize:
            case FT.FuncTranslate:
                return new StringFunctions(root.TypeOfFunction, ProcessArguments(root.ArgumentList, out props));
            case FT.FuncNumber:
            case FT.FuncSum:
            case FT.FuncFloor:
            case FT.FuncCeiling:
            case FT.FuncRound:
                if (root.ArgumentList != null && root.ArgumentList.Count > 0) {
                    return new NumberFunctions(root.TypeOfFunction,
                        ProcessNode((AstNode)root.ArgumentList[0], Flags.None, out props)
                    );
                } else {
                    return new NumberFunctions(Function.FunctionType.FuncNumber, null);
                }
            case FT.FuncTrue:
            case FT.FuncFalse:
                return new BooleanFunctions(root.TypeOfFunction, null);
            case FT.FuncNot:
            case FT.FuncLang:
            case FT.FuncBoolean:
                return new BooleanFunctions(root.TypeOfFunction,
                    ProcessNode((AstNode)root.ArgumentList[0], Flags.None, out props)
                );
            case FT.FuncUserDefined:
                needContext = true;
                if (! allowCurrent && root.Name == "current" && root.Prefix.Length == 0) {
                    throw XPathException.Create(Res.Xp_CurrentNotAllowed);
                }
                if (! allowKey && root.Name == "key" && root.Prefix.Length == 0) {
                    throw XPathException.Create(Res.Xp_InvalidKeyPattern, query);
                }
                qy = new FunctionQuery(root.Prefix, root.Name, ProcessArguments(root.ArgumentList, out props));
                props |= Props.NonFlat;
                return qy;
            default:
                throw XPathException.Create(Res.Xp_NotSupported, query);
            }
        }

        List<Query> ProcessArguments(ArrayList args, out Props props) {
            int numArgs = args != null ? args.Count : 0;
            List<Query> argList = new List<Query>(numArgs);
            props = Props.None;
            for (int count = 0; count < numArgs; count++) {
                Props argProps;
                argList.Add(ProcessNode((AstNode)args[count], Flags.None, out argProps));
                props |= argProps;
            }
            return argList;
        }

        private int parseDepth = 0;
        private const int MaxParseDepth = 1024;

        private Query ProcessNode(AstNode root, Flags flags, out Props props) {

            if (++parseDepth > MaxParseDepth) {
                throw XPathException.Create(Res.Xp_QueryTooComplex); 
            }

            Debug.Assert(root != null, "root != null");
            Query result = null;
            props = Props.None;
            switch (root.Type) {
            case AstNode.AstType.Axis:
                result = ProcessAxis((Axis)root, flags, out props);
                break;
            case AstNode.AstType.Operator:
                result = ProcessOperator((Operator)root, out props);
                break;
            case AstNode.AstType.Filter:
                result = ProcessFilter((Filter)root, flags, out props);
                break;
            case AstNode.AstType.ConstantOperand:
                result = new OperandQuery(((Operand)root).OperandValue);
                break;
            case AstNode.AstType.Variable:
                result = ProcessVariable((Variable)root);
                break;
            case AstNode.AstType.Function:
                result = ProcessFunction((Function)root, out props);
                break;
            case AstNode.AstType.Group:
                result = new GroupQuery(ProcessNode(((Group)root).GroupNode, Flags.None, out props));
                break;
            case AstNode.AstType.Root:
                result = new AbsoluteQuery();
                break;
            default:
                Debug.Assert(false, "Unknown QueryType encountered!!");
                break;
            }
            --parseDepth;
            return result;
        }

        private Query Build(AstNode root, string query) {
            Reset();
            Props props;
            this.query = query;
            Query result = ProcessNode(root, Flags.None, out props);
            return result;
        }

        internal Query Build(string query, bool allowVar, bool allowKey) {
            this.allowVar = allowVar;
            this.allowKey = allowKey;
            this.allowCurrent = true;
            return Build(XPathParser.ParseXPathExpresion(query), query);
        }

        internal Query Build(string query, out bool needContext) {
            Query result =  Build(query, true, true);
            needContext = this.needContext;
            return result;
        }
        
        internal Query BuildPatternQuery(string query, bool allowVar, bool allowKey) {
            this.allowVar = allowVar;
            this.allowKey = allowKey;
            this.allowCurrent = false;
            return Build(XPathParser.ParseXPathPattern(query), query);
        }

        internal Query BuildPatternQuery(string query, out bool needContext) {
            Query result =  BuildPatternQuery(query, true, true);
            needContext = this.needContext;
            return result;
        }
    }
}
